Wire up audio packet loss to BWE.

webrtc/audio/audio_send_stream.h

Index: webrtc/audio/audio_send_stream.h
diff --git a/webrtc/audio/audio_send_stream.h b/webrtc/audio/audio_send_stream.h
index 05ed3aaeb8cfb7697e0ea8d54a934ea5fb2d2b45..5ee49da91a7a1469285d1fcf675c39c53a43ac5c 100644
--- a/webrtc/audio/audio_send_stream.h
+++ b/webrtc/audio/audio_send_stream.h
@@ -23,6 +23,7 @@ namespace webrtc {
 class CongestionController;
 class VoiceEngine;
 class RtcEventLog;
+class RtcpBandwidthObserver;
 class RtcpRttStats;
 class PacketRouter;
 
@@ -77,6 +78,7 @@ class AudioSendStream final : public webrtc::AudioSendStream,
 
   BitrateAllocator* const bitrate_allocator_;
   CongestionController* const congestion_controller_;
+  std::unique_ptr<RtcpBandwidthObserver> bandwidth_observer_;
 
   RTC_DISALLOW_IMPLICIT_CONSTRUCTORS(AudioSendStream);
 };